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New Study Finds Marine Scrubbers Can Be More Environmentally Friendly Than Low-Sulfur Fuels

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Hedwig Oldendorff vessel at the Port of Taicang, China, prior to the start of the emission monitoring voyage. Credits: Photo: Courtesy of Patricia Stathatou

A new study led by researchers from MIT, Georgia Tech, and other institutions suggests that the use of marine scrubbers—devices that clean sulfur emissions from exhaust gases—may be just as environmentally friendly, if not more so, than burning low-sulfur fuels. This groundbreaking research, published in Environmental Science and Technology, challenges the common assumptions about the environmental impact of scrubbers and has important implications for the future of the maritime industry.

The 2020 mandate by the International Maritime Organization (IMO) to cap the sulfur content of marine fuels at 0.5% pushed shipping companies to consider alternatives to the traditionally used heavy fuel oil (HFO), which contains much higher levels of sulfur. The options? Companies could either burn low-sulfur fossil fuels, install exhaust gas cleaning systems (scrubbers), or switch to biofuels. While the latter has been limited by availability, scrubbers became the go-to solution for many, thanks to their cost-effectiveness and ability to enable continued use of cheaper, high-sulfur fuels.

However, a critical question remained: How “green” are scrubbers when viewed through a holistic environmental lens?

“Scrubbers Turned Out to Be an Unexpectedly Deep and Important Transitional Issue”

According to Neil Gershenfeld, MIT professor and senior author of the study, the study explored this question through a comprehensive lifecycle assessment. “In our collaboration with Oldendorff Carriers to broadly explore reducing the environmental impact of shipping, this study of scrubbers turned out to be an unexpectedly deep and important transitional issue,” he explained.

The Study: A Comprehensive “Well-to-Wake” Assessment

The researchers used a “well-to-wake” approach, which examines the environmental impact of fuels and technologies from production to final use. They looked at everything from the manufacturing and transportation of fuels to their emissions when burned on ships. They also gathered data directly from a bulk carrier vessel in China that burns heavy fuel oil with a scrubber and low-sulfur fuel under similar conditions. The team analyzed emissions from the exhaust and samples of washwater discharged from the scrubbers, which is often a concern due to its potential toxicity.

Lead author Patricia Stathatou, an assistant professor at Georgia Tech, emphasized that a full lifecycle analysis is critical for understanding the true environmental impact. “If we just look at everything that happens before the fuel is bunkered onboard the vessel, heavy fuel oil is significantly more low-impact, environmentally, than low-sulfur fuels,” Stathatou said. She added that scrubbers, with a lifetime of about 20 years, have a minimal environmental footprint compared to the energy-intensive production of low-sulfur fuels.

Surprising Findings: Scrubbers Surpass Low-Sulfur Fuels in Several Areas

The results of the study were surprising. When the researchers considered the entire lifecycle, including the production of fuels and scrubbers, burning heavy fuel oil with scrubbers was found to be the least harmful option in terms of most environmental factors, such as greenhouse gas emissions, terrestrial acidification, and ozone formation.

“The claims about environmental hazards and policies to mitigate them should be backed by science,” said Stathatou. “You need to see the data, be objective, and design studies that take into account the full picture to be able to compare different options from an apples-to-apples perspective.”

Scrubbers: A Proven and Mature Technology

Marine scrubbers, which have been used for decades in land-based applications like power plants, are now widely deployed in the shipping industry. Scrubbers are typically large vertical tanks that use seawater to wash sulfur dioxide from the exhaust gases. The seawater reacts with the sulfur, converting it into sulfates, which are environmentally benign. The washwater is then released back into the ocean, where it is diluted by the vast expanse of seawater.

Despite concerns over the acidity and potential pollutants in the washwater, the study found that most chemical concentrations in the washwater were well below the limits set by environmental regulations, such as those from the U.S. Environmental Protection Agency and the European Union.

Scrubbers Meet International Standards

The researchers also tested the washwater for over 60 chemical parameters, including metals and hydrocarbons, and found that concentrations of harmful substances were generally well within safe levels. “Scrubbers reduce sulfur dioxide emissions by 97 percent, making them just as effective as low-sulfur fuels in terms of sulfur emissions,” said Scott Bergeron, managing director of Oldendorff Carriers, who co-authored the study.

A Call for Balanced Environmental Policies

This research has significant implications for future maritime environmental policies. As Stathatou points out, there is growing momentum toward alternative fuels, but it’s critical to assess the environmental impacts of these fuels in comparison to current technologies. “We must do our due diligence to compare them equally with existing solutions to see the costs and benefits,” she said.

The study’s findings could reshape policies governing the maritime industry, suggesting that scrubbers may offer a more sustainable path forward than previously thought. The research team hopes this will prompt a more science-driven approach to reducing shipping’s environmental footprint.

The study, which includes contributions from researchers at MIT, Georgia Tech, and Oldendorff Carriers, highlights the importance of scientific analysis in shaping policies that reduce the environmental impact of global shipping. With over 5,800 vessels now using scrubbers worldwide, the technology is clearly making an impact, but questions around its long-term environmental effects are only just beginning to be answered.

EP Staff is the editorial team at EdPublica, an independent media organisation focused on science, education, environment and public policy. The team produces evidence-based news, features, explainers and analysis on issues that shape society and everyday life.

Climate & Environment

Global Ecosystem Restoration Progress Falls Short of 2030 Targets, UN Report Warns

Jishnu P

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Aerial view of a winding river flowing through dense green vegetation and a restored-looking natural landscape.
An aerial photograph showing a river winding through lush green vegetation, with patches of open land and dense tree cover along its banks. The image illustrates the ecological value of freshwater ecosystems and the role of landscape conservation and restoration in protecting biodiversity.

Ecosystem restoration efforts are expanding across the world, but progress remains insufficient to meet global biodiversity targets for 2030, according to a new report released by the Food and Agriculture Organization of the United Nations (FAO), the United Nations Environment Programme (UNEP) and the Secretariat of the Convention on Biological Diversity (SCBD).

The report, Restoration Progress Report: Nature’s Comeback – Scaling Ecosystem Restoration for People and Planet, documents approximately 252 million hectares of terrestrial, freshwater, marine and coastal ecosystems under restoration across 149 countries in 2026. Despite this progress, the report warns that implementation must triple to achieve the global commitment to restore 30 per cent of degraded ecosystems by 2030.

Countries have collectively committed to restoring approximately one billion hectares through national plans, international agreements and regional initiatives. However, the documented restoration area represents only about a quarter of these commitments, highlighting the gap between political ambition and action on the ground.

The assessment comes as the United Nations Decade on Ecosystem Restoration (2021–2030) enters its second half. It examines restoration progress across different ecosystems, the financial resources required and the measures needed to accelerate recovery.

The report identifies land-use change, agricultural expansion, deforestation, overexploitation of natural resources, pollution and climate change as major drivers of ecosystem degradation. These pressures frequently interact, making recovery more difficult and expensive.

More than 1.56 billion hectares of land, representing over 15 per cent of the global land surface, are estimated to be degraded. Between 2015 and 2019, at least 100 million hectares of previously healthy and productive land were degraded annually. Agricultural lands account for more than 60 per cent of global land degradation, with an estimated 480 million hectares of cropland and 560 million hectares of pastureland affected.

Freshwater and marine ecosystems lag behind

Restoration progress varies considerably across ecosystem types. Terrestrial ecosystems account for the largest share of documented restoration, with approximately 232 million hectares under restoration. However, this still represents only about half of the 469 million hectares estimated to be required to meet the 2030 restoration target for terrestrial ecosystems.

Freshwater ecosystems face a substantially larger implementation gap. Only around 11 million hectares are documented as being under restoration, representing approximately 4.5 per cent of the estimated 244 million hectares required to meet the target.

Marine and coastal ecosystems have approximately 5.7 million hectares under restoration, equivalent to around 23 per cent of their estimated 25 million-hectare target.

The report notes that freshwater and marine ecosystems are among the most rapidly degrading environments, despite their importance in supporting biodiversity, food security and livelihoods. Incomplete monitoring and inconsistent national reporting also make it difficult to establish the full extent of restoration activities in these ecosystems.

Funding gap threatens restoration ambitions

Financing remains another major obstacle. Global restoration investments reached approximately $64 billion in 2022, but annual funding needs to increase to $296 billion by 2030 and $448 billion by 2050 to meet restoration requirements.

The report calls for greater public investment alongside private and blended financing mechanisms. It also stresses the need to redirect financial flows and subsidies that encourage unsustainable resource use and contribute to environmental degradation.

Beyond ecological benefits, restoration could generate significant employment opportunities. The report estimates that more than one million green jobs have been created through the World Restoration Flagships, while ecosystem restoration has the potential to generate over 32 million additional jobs globally by 2030.

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Vibrant green moss and plants beside a gently flowing stream in a natural setting.Image credit:Pexels

It also highlights the potential of restoration to address climate change and biodiversity loss. Research cited in the assessment indicates that restoring just 15 per cent of global priority areas could capture and store carbon equivalent to 30 per cent of the total increase in atmospheric carbon dioxide since the Industrial Revolution, while helping avoid 60 per cent of species extinctions.

The report emphasises that successful restoration requires more than increasing the area of land brought under recovery. It calls for greater participation of Indigenous Peoples and local communities, recognition of land rights, stronger monitoring systems and restoration strategies that address entire landscapes and ecosystems.

As the 2030 deadline approaches, the assessment identifies three priorities for accelerating progress: building a broader global movement for restoration, strengthening political commitment and developing the technical capacity needed to implement and monitor restoration programmes.

It concludes that restoration targets must translate into sustained ecological recovery rather than remain numerical commitments. Preventing further degradation and ensuring that restored ecosystems continue to recover will be essential to securing long-term benefits for biodiversity, climate resilience and human well-being.

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Greener Forests, Weaker Carbon Sinks? Study Finds Declining Productivity in Northeast India

A 24-year satellite-based study finds that Northeast India’s forests are experiencing declining carbon productivity despite relatively stable canopy cover, highlighting how rising atmospheric dryness could weaken their capacity to absorb and retain carbon.

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Dense green forest canopy with sunlight filtering through the leaves of tall trees.
A dense forest canopy illustrating the vegetation cover and ecological richness of tropical forest ecosystems.Image credit:Pexels

Forests in Northeast India are showing signs of a weakening capacity to accumulate carbon despite maintaining relatively stable canopy cover, according to a study published in Ecological Indicators in October 2026. The research suggests that increasing vegetation greenness does not necessarily indicate stronger carbon sinks, highlighting the need to assess forest health beyond satellite measurements of green cover.

Titled Are Greener Forests Stronger Carbon Sinks? Rising Vapour Pressure Deficit Instigates Greening-Productivity Decoupling in a Tropical Biodiversity Hotspot in India, the study examined forest carbon dynamics across Northeast India using 24 years of satellite-derived data from 2001 to 2024.

Researchers analysed three indicators: Leaf Area Index (LAI), Gross Primary Productivity (GPP) and Net Primary Productivity (NPP). These measurements helped assess changes in forest canopy structure, photosynthetic activity and the amount of carbon retained in plant biomass after accounting for plant respiration.

The analysis found that while canopy structure remained relatively stable and gross primary productivity increased modestly by 1.76 grams of carbon per square metre annually, net primary productivity declined by 0.83 grams of carbon per square metre annually across much of the region.

The researchers identified a divergence between canopy greenness and carbon productivity across approximately 40% of forested areas. A separate divergence between photosynthetic activity and net productivity was observed across around 30% of the region.

These findings indicate that forests can maintain their green appearance without achieving corresponding gains in carbon accumulation.

Atmospheric dryness emerges as a major factor

The study identified rising Vapour Pressure Deficit (VPD) as a primary driver of declining forest productivity. VPD measures the difference between the amount of moisture the atmosphere can hold and the moisture it actually contains. Higher VPD indicates greater atmospheric demand for water, increasing stress on vegetation.

Under such conditions, plants may close their stomata, the small pores on their leaves, to reduce water loss. This also restricts the intake of carbon dioxide required for photosynthesis, potentially reducing the amount of carbon absorbed by vegetation.

The researchers also identified a major shift in forest carbon functioning beginning around 2012. Their analysis suggests that the relationship between canopy structure, photosynthesis and net carbon accumulation has weakened over time.

The findings are particularly significant for Northeast India, which the study identifies as a climatically sensitive biodiversity hotspot containing approximately one-third of India’s forest carbon.

Earlier research points to similar concerns

The findings build on earlier research published in Scientific Reports in December 2023, which examined vegetation productivity across India between 2001 and 2019.

That study found that India’s Leaf Area Index increased by 6.75% in consistently forested areas, while Net Primary Productivity declined by 6.19%. Northeast India, the Western Ghats and parts of Peninsular India emerged as important regions experiencing declining productivity.

The 2023 research associated these changes with rising temperatures, which can reduce photosynthesis and increase plant respiration beyond certain temperature thresholds.

Another study examining a semi-deciduous forest in Kaziranga, published in Agricultural and Forest Meteorology in 2022, demonstrated how carbon exchange varies with seasonal and climatic conditions. It found that the forest functioned as a carbon sink during the pre-monsoon season but as a carbon source during winter in the observed study period.

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Image of a dense forest alongside a flowing river.Image credit:Pexels

Together, these studies highlight the importance of examining forest productivity, atmospheric conditions and seasonal carbon exchange rather than relying solely on changes in green cover.

The latest research does not suggest that Northeast India’s forests are structurally collapsing. Instead, it points to a less visible change in their ecological functioning, with implications for forest carbon accounting and climate-resilient forest management.

The findings underline the need for monitoring systems that combine satellite observations with measurements of atmospheric stress and carbon productivity to better understand how tropical forests respond to a warming climate.

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252 Million Hectares Under Restoration Across 149 Countries, but UN Warns of 2030 Target Gap

A UN report finds that 252 million hectares across 149 countries are under ecosystem restoration. However, increased investment and accelerated action are needed to meet global restoration targets by 2030.

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River flowing through a forested mountain landscape with evergreen trees and snow-covered peaks.
Healthy mountain forests and river ecosystems play an important role in maintaining biodiversity and ecological balance.Image credit:Pexels

Global efforts to restore degraded ecosystems have reached 252 million hectares across 149 countries, generating more than one million green jobs. However, a new United Nations assessment warns that restoration efforts remain insufficient to meet international biodiversity targets by 2030, calling for a more than fourfold increase in annual investment.

The findings are presented in the Restoration Progress Report: Nature’s Comeback – Scaling Ecosystem Restoration for People and Planet, released on October 29, 2026, by the United Nations Environment Programme (UNEP), the Food and Agriculture Organization (FAO) and the Secretariat of the Convention on Biological Diversity (CBD).

The report provides the first comprehensive global assessment of progress towards commitments to restore approximately one billion hectares of degraded ecosystems. These commitments are linked to the UN Decade on Ecosystem Restoration (2021–2030) and the Kunming-Montreal Global Biodiversity Framework, which calls for at least 30 per cent of degraded terrestrial, freshwater, marine and coastal ecosystems to be under effective restoration by 2030.

According to the assessment, the 252 million hectares currently documented under restoration represent the largest recorded global restoration effort. However, this accounts for only 34 per cent of the indicative global benchmark associated with the 2030 target.

Freshwater and marine ecosystems lag behind

The report identifies considerable differences in restoration progress across regions and ecosystem types. Asia accounts for the largest share of documented restoration, with 192.2 million hectares, followed by Africa with 36.3 million hectares and Europe with 9.1 million hectares. North and Central America account for 5.8 million hectares, South America 5.4 million hectares and Oceania 3.2 million hectares.

However, the report cautions that these figures should not be interpreted as a ranking of restoration performance, as they also reflect differences in regional land area and monitoring and reporting capacities.

Restoration of terrestrial ecosystems has reached nearly half of the global 2030 target. China reports the largest terrestrial restoration area, with 127.4 million hectares, while substantial restoration activities have also been documented in Mongolia and Kazakhstan.

Progress remains considerably slower in freshwater, marine and coastal ecosystems, despite these environments experiencing rapid degradation.

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A river along the side of a dense forest. Image credit: Pexels

The assessment documents 11 million hectares of freshwater ecosystems under restoration across 62 countries and 5.7 million hectares of marine and coastal ecosystems across 46 countries. The report also notes that limited monitoring and reporting may mean that actual restoration activities in these ecosystems are higher than the documented figures.

Meanwhile, the share of countries reporting implemented wetland restoration or rehabilitation programmes has increased from 8 per cent in 2022 to 54 per cent.

Restoration financing needs to increase fourfold

Insufficient investment remains a major obstacle to achieving global restoration commitments. The report estimates that annual restoration financing must increase from US$64 billion to US$296 billion by 2030, representing more than a fourfold rise.

Agroforestry requires the largest estimated annual investment, at US$87 billion, followed by restorative reforestation at US$52 billion, peatland restoration at US$44 billion and seagrass restoration at US$28 billion.

The report identifies employment generation as another potential benefit of scaling up restoration. While more than one million green jobs have already been associated with restoration initiatives, increased global investment could generate up to 32 million additional jobs by 2030.

It also highlights the potential contribution of ecosystem restoration to climate mitigation and biodiversity protection. Research cited in the assessment indicates that restoring just 15 per cent of global priority areas could capture and store 30 per cent of carbon dioxide-equivalent emissions released since the Industrial Revolution and help prevent 60 per cent of projected species extinctions.

The report further identifies the participation and leadership of Indigenous Peoples and local communities as essential to ensuring long-term restoration outcomes. Secure land rights, stronger monitoring systems and sustained political commitment are among the priorities identified.

With five years remaining in the UN Decade on Ecosystem Restoration, the assessment calls on governments to move beyond isolated restoration projects towards coordinated, long-term programmes that address the underlying causes of ecosystem degradation.

It emphasises that the 2030 targets should serve as a milestone in the restoration process rather than its conclusion, as ecological recovery requires sustained action and investment beyond the end of the decade.

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